Poly(hexahydrotriazine)s are thermosetting polymers having good Young's moduli, solvent resistance, and resistance to environmental stress cracking as disclosed by Garcia et al. in Science Vol. 344, pages 732-735. However, their applications have been limited because of the challenges encountered in making the polymers as well as forming large molded parts from the polymers. The current methods of making poly(hexahydrotriazine)s involve mixing reactants in one homogeneous phase. The reaction is not readily scalable. In addition, a gel can be formed trapping solvents inside. Therefore, poly(hexahydrotriazine)s are typically made into films to facilitate solvent evaporation. Accordingly, the industry is always receptive to improved methods of making poly(hexahydrotriazine)s that is readily scalable. It would be a further advantage if poly(hexahydrotriazine)s can be readily molded to articles having various forms.